1. Field of the Invention
The present invention relates to a nonreciprocal circuit device, such as an isolator, used in a microwave band, or the like and to a communication apparatus including this isolator.
2. Description of the Related Art
A conventional two-port type nonreciprocal circuit device has been constructed by discretely preparing circuit elements such as capacitors and resistors, and disposing them at predetermined positions on a printed board, installing them, and disposing, on the printed board, a ferrite assembly which comprises a ferrite and two central conductors arranged on the ferrite so as to intersect each other.
The above-described capacitor has been constructed by forming electrodes on both surfaces of a dielectric substrate, and then cutting out the electrodes into a predetermined size. As a resistance element, an ordinary chip resistor has been used.
In conventional two-port type nonreciprocal circuit device, correctly disposing circuit elements at predetermined positions on a printed board and installing them, requires numerous processes and a great deal of man-hours, and makes mass-production at a low cost difficult. In addition, since it is necessary to vary the capacity value of each of required capacitors in accordance with the operating frequency or the application of a nonreciprocal circuit device, the variety of cut-out sizes of dielectric substrate increases, so that the management of capacitor elements becomes complicated. Furthermore, since numerous circuit elements are installed, connection points increases, resulting in a reduced reliability. Moreover, since it is necessary to provide the area needed to dispose these circuit elements on the printed board, the printed circuit is difficult to reduce its size. This makes it difficult to meet the market demand for miniaturization of the nonreciprocal circuit device.
Accordingly, it is an object of the present invention to solve the above-described problems by eliminating the need to mount the above-described circuit elements onto a printed board, and to provide a nonreciprocal circuit device which allows mass production thereof at a low cost, which eliminates complicatedness of the management of capacitor elements, which facilitates the securing of reliability by reducing connection points, and which allows an reduction in the overall size thereof by the reduction in the area of a substrate.
The invention provides a nonreciprocal circuit device, comprising a ferrite assembly consituted by combining a ferrite and first and second central conductors which are arranged so as to mutually intersect in a state of being electrically insulated from each other, a magnet applying an magnetostatic field to the ferrite assembly, a yoke, and circuit elements which are connected to the first and second central conductors and which constitute a matching circuit. In this nonreciprocal circuit device, the circuit elements are constituted of a dielectric body of a dielectric laminated substrate on which said ferrite assembly is mounted, and electrodes provided on predetermined layers of the dielectric laminated substrate.
Thus forming circuit elements constituting a matching circuit in the substrate on which the ferrite assembly is mounted, solves the above-described problems involving in mounting discrete chip-shaped capacitors and chip resistors onto a printed board.
In the nonreciprocal circuit board in accordance with the present invention, preferably, a plurality of capacitors is formed within the dielectric laminated substrate. Particularly in a two-port type nonreciprocal circuit device, by incorporating numerous capacitors required for a matching circuit into a single dielectric laminated substrate, the mass-productivity is increased, the complicatedness of the management of capacitor elements is eliminated, the reliability is improved, and thereby the effects of overall size-reduction and cost-reduction are enhanced.
Also, in the present invention, preferably, the dielectric laminated substrate has a recess or a hole at which the ferrite portion of the ferrite assembly is engaged with the dielectric laminated substrate. This facilitates the fixing of the ferrite assembly to within the nonreciprocal circuit device, eliminates the need for special members for fixing, and reduces the overall height by the dimension of the ferrite portion engaged into the above-described recess or hole.
Furthermore, in the present invention, it is preferable that the ferrite assembly be formed by winding each of the central conductors around the ferrite, and that the dielectric laminated substrate have a recess or a hole at which the central conductor portion of the ferrite assembly is engaged into the dielectric laminated substrate. Thereby, the fixing of the ferrite assembly to within the nonreciprocal circuit device is facilitated, and the overall height of the nonreciprocal circuit device is reduced by the dimension of the central conductor portion engaged into the above-described recess or hole.
Moreover, in the present invention, it is preferable that the ferrite assembly, the magnet, and the yoke be arranged on the dielectric laminated substrate in this order, that through hole electrodes be provided in the side surfaces of the dielectric laminated substrate, and that projections provided on the yoke are engaged into the through hole electrodes. This arrangement facilitates the ground connection of the dielectric laminated substrate and yoke, and prevents the connection portions from projecting outside from the side surfaces of the dielectric laminated substrate.
Also, in the present invention, preferably, the projections of the yoke and the through hole electrodes are soldered together, whereby electric and mechanical coupling are simultaneously achieved.
Furthermore, in the present invention, preferably, electrodes to be connected to the central conductors are provided on the top surface of the dielectric laminated substrate. Thereby, the central conductors of the ferrite assembly can be easily surface-mounted on the top surface of the dielectric laminated substrate.
In addition, in the present invention, preferably, electrodes to be connected to external circuits are provided on the bottom surface of the dielectric laminated substrate. This allows these electrodes to be used as terminals when the nonreciprocal circuit device is surface-mounted onto the circuit board on which it is to be mounted.
Moreover, the present invention provides a communication apparatus which uses a nonreciprocal circuit device comprising any one of the above-described constructions, and which is provided in, for example, the output section of the circuit for amplifying transmitted signals.